Matching a sub to single driver speakers

[bigjppop]

So I've really enjoyed my first foray into single driver speakers (some Omega 3's) and I'm loving all the things they do right, now I'm thinking I just need to find a good subwoofer to match to them. I've read a lot of threads in this forum about "x or y is a fantastic full range driver but if you need low bass you might want to add a sub." I'm just wondering if there is a "go-to" sub design that you single driver guys/gals like.

It seems that most of the full range drivers that I've been looking at at dropping off pretty quickly below 50 Hz (mostly in the 4.5-6 inch range) and while I don't need a sub that drops into the teens, something that goes into the mid 20's would be nice. I don't need to blast out any windows or win any SPL contests; basically I'm looking for a sub that picks up where a good full range driver drops off. I would still like speed, clarity, etc, I just want it to go a little lower.

Any thoughts are much appreciated.

[rjbond3rd]

Speaking strictly as a newb, you want a sub that will complement room gain (the tendency of the room to boost low frequencies at about ~3db per octave but that's room-dependent). An EBS (extended bass shelf) that rolls off at approximately 3 db per octave will match nicely (yielding an approximately flat response, ignoring room modes). A sealed sub is also pretty good, rolling off at 6 db per octave.

Personally, I'm looking at maybe a couple CSS SDX7's in two sealed cabs. The EBS is trickier to get right.

The ultimate, though, is a tapped horn, to my newbie ears. Serenechaos has a pair of 7-foot-tall cabs that are just /incredible/ and not boomy at all. But they are quite large compared to, say, a small sealed box.

[Jim Shearer]

You might look into an OB using a large, high QTS drivers, a la MJK's H-frames using either the Eminence Alpha 15a or the 18" Goldwood. Check it out at Quarter Wavelength Loudspeaker Design

Cheers, Jim

[rjbond3rd]

Jim, right on! Subs are hard to get right, and OB bass is so much easier (no booming of the room modes). I am psyched to build MJK's JX92S/Goldwood passive this spring, when it's warm outside.

[Godzilla]

I really like the way my H-frames sound and would recommend building a pair to use with your Omegas. They enhance the bass of my BIBs. I prefer the H-frame sound to the sealed sub i used to use.

Godzilla

[chrisb]

As mentioned in other threads, I recently finished reading Floyd E Toole's recent text on "Loudspeakers and Rooms", and while he's mostly focused on true multichannel audio (as in Home Theater) "done right", some of his observations regarding low frequency performance would no doubt apply to 2 channel audio.

The most salient points for me were that below the room's transition frequency (usually higher than the 80Hz often used as a default for surround system XO ), the room is pretty much in control (we probably already knew that); successful acoustic treatment of low frequency anomalies can consume a lot of space and materials; and finally, the number of woofers and locations required for even distribution of bass throughout even smallish rooms is not necessarily what has been standard practice in the past - a pair of woofers will often perform best on the side walls, rather than in the corners or under the "mains".

I certainly agree that the CSS SDX7 can deliver great performance in a small box (as small as less than 1 cu ft), but if more than 2 woofers are implemented, there are lower cost alternatives.

[rjbond3rd]

Chris, I'm sure you're right that there are lower-cost options to using multiple SDX7's sealed but they're just so compact! Still, for me personally, subs have always been an exercise in frustration. Aside from Serenechaos' tapped horns, I've actually never heard deep bass that was completely right. Here's looking forward to the Goldwood's!

Godzilla, can you describe your BiB / H-frame setup, e.g. number of H-frames, number of drivers per H-Frame, position relative to the BiB, and whatever low-pass / high-pass you're doing?

[planet10]

I always look for something that is more of a midbass than a subwoofer -- something that has good HF extension. And you should always aim for a pair (Toole's book makes it pretty clear why)

The SDX7 is one of my very favorite bass drivers. Used as a woofer somewhere between 14-21 litres sealed net (including volume faking by damping material), but you could get away with as little as 7 litre. We built a number of exactly 12" cubes with a built-in Foster plate amp. Very versatile, very simple. The SDX7 is fairly expensive thou, and needs at least minimal treatment before use.

If you can live with about 2x the volume the less expensive CSS Trio8 has huge bang for the buck.

ApexJr Super8, or Silver Flute 8" if you are on a real tight budget.

I have Alpha 15 and the Goldwood 18. I'm a bit leary of the 18 in the H frame, the enclosure itself limits the HF performance. But we won't really know till we try it.

dave

[InclinedPlane]

OB subs are the ONLY subs, IMO. But I don't like high-mass drivers. And don't use regular plate amps if you can possibly help it. Their sound is as tubby as the subs they are meant for. Use the best fullrange amp you can afford, and passively XO.

[bigjppop]

I really appreciate all the responses. I must say, after doing some research on the SDX7, I'm pretty shocked; I don't think anyone has ever recommended me a 6.5 inch sub! You guys really like it that much?

A small size would be nice, but is not absolutely necessary. Also, I've never heard, or even seen in real life, OB subs so maybe that would be something to consider as well.

It does sound like everyone recommends at least two subs; you like two small subs vs. one larger one?